This application claims the benefit of International Application Number PCT/SE99/01897, which was published in English on May 18, 2000.
The present invention relates to a method and a device for controlling temperature in a certain space, more specific, for automatic regulation of temperature in a refrigerator and/or freezer cabinet having thermostat-controlled operation.
Mechanical and electronic thermostats of today have fixed connect temperature (the refrigerating machine is turned on) and disconnect temperature (the refrigerating machine is switched off) . This implies that the average temperature of the refrigerated space is controlled by setting a desired temperature, i.e. by manually moving (the setting means for) connect and/or disconnect temperature upwards or downwards. These connect and disconnect temperatures have been chosen after tests (carried out) on a limited number of prototypes, and the average temperature of the (refrigerated) space can vary from one application to another, based on constructive disparities. The variations in the ambient temperature, and/or atmospheric pressure, can furthermore result in different temperatures in the refrigerated space, at the same connect and disconnect temperatures set, particularly when the connect and disconnect temperatures are (measured as) evaporator temperature. There is no feed-back coupling; the temperature of the (refrigerated) space do not influence the connect and disconnect temperatures.
A problem which the present invention solves is that it can keep a temperature set in the (refrigerated) space. Another problem the invention solves is that it automatically adjusts the temperature to the set temperature.
The object of the present invention is to control the temperature in a refrigerating application, which performs its function thermostatically in a manner resulting in that the average temperature in the refrigerated space, during a period, is equal to the set temperature (preset temperature.
The present invention has reference to automatic regulating the temperature of the space, which temperature varies over the time. The temperature of the space drops as the refrigerating machine generates coldness, and rises when the refrigerating machine does not.
The system aims at getting an average temperature equal to a preset temperature. In the beginning the system measures a temperature in the space several times during the course of a period, in order to get the average temperature during that period. The system has a connect and a disconnect temperature to control the operation of the refrigerating machine, so that the average temperature will be equal to the preset temperature. This is attained by moving the connect and/or disconnect temperatures upwards or downwards, depending on the difference between the average temperature of the space and the preset temperature. This removal of the connect and/or disconnect temperatures, make the system aiming at an average temperature, which after the next period or periods is equal to the preset temperature. The difference between the average temperature of the period and the preset temperature is a discrepancy, which act to cancel the difference itself. In case the discrepancy between the period""s average temperature and the preset temperature is greater than a certain discrepancy value, the connect and/or disconnect temperatures are moved upwards or downwards in order to cancel the difference, and subsequently get an average temperature equal to the preset for the next period or periods.
In principle the system works in the following manner: The automatic system for temperature regulating checks the operation of the refrigerating machine. The refrigerating machine can be of different kinds, i.e. of absorption or compression type. The system notice a regulating temperature within a certain periodicity, and compares this with current connect and disconnect temperatures. The refrigerating machine is turned on when the regulating temperature rises above the connect temperature and switched off when the regulating temperature drops below the disconnect temperature. The refrigerating machine is run thermostatically by means of a thermostat function characterized in the above mentioned connect and disconnect temperatures. The temperature of the refrigerated space, which is the controlled temperature, varies under stable conditions during a period. The system carries out a continuous calculation of the average temperature value in the refrigerated space within a period, designated xe2x80x9cjxe2x80x9d. A complete period comprises one xe2x80x9conxe2x80x9d time interval Pon and one xe2x80x9coffxe2x80x9d time interval Poff. The latest calculated average temperature, at the end of the period, is the average temperature of the period. The system calculates a discrepancy between the average temperature and the preset temperature. When the discrepancy is greater than a predetermined value for discrepancies, the temperature for connect and/or disconnect are changed according to a predetermined standard, to have the discrepancy reduced below the predetermined value.
This invention can be used in all refrigerating applications (based on whatever refrigerating technique), which generate coldness within a certain space, and which functions thermostatically, e.g. as controlling electronics to an absorption wine refrigerator cabinet.
The present invention keeps the refrigerated space at an average temperature essentially equal to the preset temperature, independent of differences in constructions between the applications (space, thermostat, and so on) and variations in the ambient temperature.
An advantage of the present invention is that the average temperature of the refrigerated space influences the connect and/or disconnect temperatures, i.e. there is a feed-back. A further advantage oc the present invention is that the system in itself adjusts the connect and/or disconnect temperatures, as the ambient temperature varies, whereby heat leakage variations will be compensated for, and the refrigerated space countinues having an average temperature essentially equal to the preset temperature.